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Question: Answered & Verified by Expert
An asteroid of mass m is approaching earth, initially at a distance 10Re with speed vi. It hite oarth with a speed vf , Re and Me are radius and mass of earth), then
PhysicsGravitationJEE Main
Options:
  • A vf2=vi2+2GmRe1+110
  • B vf2=vi2+2GMeRe1+110
  • C vf2=vi2+2GMeRθ1-110
  • D vf2=vi2+2GmRe1-110
Solution:
2941 Upvotes Verified Answer
The correct answer is: vf2=vi2+2GMeRθ1-110

Initial energy of the asteroid is
Ei=Ki+Ui=12mvi2-GMθm10Re

Final energy of the asteroid,
Ef=12mvf2-GMθmRθ

According to law of conservation of energy, Ei=Ef

12mvi2-GMθm10Rθ=12mvf2-GMθmRθ

vf2-2GMθRθ=vi2-2GMθ10Rθ

 vf2=vi2+2GMθRθ1-110

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